抄録
To monitor the crustal deformation associated with the Usu volcano unrest from 27th March, 2001, we started GPS observations from 28th March, 2001 using Ashtech Z-XII receivers. We succeeded installing 6 new continuous stations around the volcano before the beginning of the eruption at 13:07 (JST), 31st March, 2000. Data were collected via a cellular-phone telemetry system. We carried out automatic rapid data analysis every 3 hours using the Bernese GPS Software Version 4.2, Bernese Processing Engine and IGS predicted ephemeredes. Results were published immediately on the WWW server at Hokkaido University to monitor the volcanic activity. From our GPS observations, we find that: (1) cumulative horizontal displacements from 29th March to noon of 31st March, 2000 exceeded 1 m at the KON, OHD, UVO stations, (2) just before the beginning of the eruption, striking deformation was observed at KON located right above the new crater, (3) after the beginning of the eruption, large scale crustal deformation was generally terminated
